A power conditioning system with a fuel cell is known in which output power of the fuel cell can be supplied to a load connected to the fuel cell by supplying fuel gas (e.g. hydrogen) and oxidant gas (e.g. air) to the fuel cell according to a request of the load.
In the power conditioning system as described above, a high-voltage battery is normally provided in parallel with the fuel cell with respect to the load. This battery assists power generated by the fuel cell by outputting stored power to the load in response to a request of the load.
In such a power conditioning system, converters for converting each output voltage at a predetermined required voltage ratio may be provided between the fuel cell and the load and between the battery and the load on the basis of a voltage required by the load, an outputtable voltage of the fuel cell and a charge voltage of the battery.
JP5143665B discloses a power system in which a fuel cell and a battery are provided in parallel with respect to a load and a converter is provided at each of output sides of the fuel cell and the battery. This power system is configured to control at least one of output currents of the fuel cell and the battery by the converter for the other.
Further, in the case of installing a power conditioning system in a vehicle, regenerative power is generated if a drive motor performs a regeneration operation during downhill running or deceleration of the vehicle. This regenerated power is utilized to charge a battery on the basis of a state of charge of the battery. As just described, a current flow from the battery to a load and a current flow from the load to the battery are generated in a battery converter.